This invention relates to a fuel injector assembly, and more particularly to a high-pressure direct injection fuel injector assembly having a seat that is thermally isolated from a body exposed to extreme temperatures within an engine cylinder.
Experimental testing has shown that the extreme temperatures within an engine cylinder can effect the operative performance characteristics of the fuel injector assembly. First, the excessive temperatures of the engine cylinder can disproportionately distort the components of the fuel injector assembly within the engine cylinder. For example, the body, which is preferably metal, can be distorted an unequal quantity relative to a needle disposed within the body. Distorting of the components of the fuel injector disproportionally can, for example, alter the dimensional tolerances between the components of the fuel injector, i.e., the body, the needle, and the seat, which is believed, under certain operative conditions, to render the fuel injector inoperative. Second, the excess temperatures of the engine cylinder can cause the fuel injector to overheat and coke unburned fuel on the components of the fuel injector, i.e., the tip components of the fuel injector, such as, the seat at an outlet portion of the body. Coking of the fuel injector tip components can block the outlet of the fuel injector, which is believed to affect the fuel spray patterns of the fuel injector. Thus, distorting and coking of the fuel injector components utilized in a direct inject application is believed to diminish the performance capability of the fuel injector. A seat that is thermally isolated from a body of a fuel injector assembly, it is believed, will substantially avoid the above-discussed problems. Thus, an arrangement of a fuel injector assembly where the seat is substantially thermally isolated from the body (i.e.—the contact area between the seat and the body is minimized) is desirable.